This is a 3-period study. Periods 1 and 2 will evaluate the effects of multiple doses of laropiprant on the antiplatelet effects of clopidogrel and aspirin administered in combination in participants with primary hypercholesterolemia or mixed dyslipidemia. Period 3 will be open-label and will evaluate single dose pharmacokinetics of nicotinic acid and laropiprant components of Tredaptive.